Gregory Ewing <greg.ew...@canterbury.ac.nz>: > Marko Rauhamaa wrote: >> Which phenomenon prevents a black hole from ever forming. Yet >> astronomers keep telling us they are all over the place. > Astronomers have observed objects whose behaviour is entirely > consistent with the existence of black holes as predicted by general > relativity.
As far as I understand, all we can ever observe is black holes in the making since the making can never (seem to) finish. IOW, the event horizon never forms. These almost-black-holes are virtually indistinguishable from black holes proper. However, we don't have to speculate about the physics of the insides of the black hole. > The singularity being talked about there is an artifact of a > particular coordinate system; the theory predicts that there is no > *physical* singularity at the event horizon. That theory can't be tested even in principle, can it? Therefore, it is not scientific. > It's true that we outside can't be absolutely sure that things are as > predicted at the horizon itself, because any observer we sent in to > check would be unable to report back. But in principle we can observe > arbitrarily close to it. The observations we've made so far all fit > the theory, and the theory doesn't present any obstacles to > extrapolating those results to the horizon and beyond, so we accept > the theory as valid. Religious theories about the afterlife face similar difficulties -- and present similar extrapolations. > There *is* a difficulty at the very center of the hole, where there is > a true singularity in the theory, so something else must happen there. > But for other reasons we don't expect those effects to become > important until you get very close to the singularity -- something on > the order of the Planck length. That's my point: such speculation must remaing mere speculation. The universe doesn't owe us an answer to a question that we can never face. Marko -- https://mail.python.org/mailman/listinfo/python-list
